In coronary bypass surgery, a partially occluded coronary artery can be bypassed by grafting a conduit to the coronary artery to supply perfusing blood, to a location downstream or distal of the occlusion. The conduit is often a saphenous vein graft or an internal mammary artery (IMA). The conduit has a distal end, to be joined distal to the occlusion, and a proximal end, to be joined to a source of perfusing blood, typically the aorta.
In a typical procedure, an incision, an arteriotomy, is made in the coronary artery distal to the occlusion. The incision often results in bleeding through the incision into the surgical field. The blood can be suctioned and/or blown away to preserve the surgeon's field of view. The distal end of the conduit can be brought to bear to the side of the coronary artery near the arteriotomy. An end-to-side anastomosis can then be performed.
In the end-to-side anastomosis, the distal end of the conduit is sewn to the side of the coronary artery over the incision. During the anastomosis procedure, the blood flow from the incision may be quite profuse. The blood may come through the original blood vessel, which may be only partially occluded. The blood may also come from the “collateral flow” of blood coming from the coronary artery distal of the occlusion. The collateral flow can come from vessels that have grown to supply the coronary artery distal of the occlusion, often in response to the occlusion.
The blood flowing from the incision is not flowing to the heart, which can result in ischemia, which can be severe. The ischemia can put additional time pressure on the surgeon. If severe, the ischemia may force the surgeon to put the patient on a blood pump where this was initially to be avoided. In some cases, a planned for minimally invasive beating heart procedure is changed into an open chest, arrested heart procedure, with the patient put onto a heart-lung machine. The blood can also flood the surgical field, interfere with the surgeon's vision, and thus interfere with, and lengthen, the anastomosis procedure.
The ischemia problem has been addressed by off-pump perfusion-assisted direct coronary artery bypass (PADCAB™) (Quest Medical, Austin Tex.), using a distal perfusion device. Medtronic (Minneapolis, Minn.) sells the QuickFlow™ DPS™ Distal Perfusion System. The distal perfusion device includes a tubular member that can be supplied at the proximal end with perfusing blood from the aorta or the femoral artery. The distal end of this device can be inserted into the incision in the artery. The blood flow through the distal perfusion device can supply the coronary artery with some perfusing blood during the anastomosis procedure. The distal perfusion device distal end can be difficult to hold in position during some surgeries, especially minimally invasive surgeries. Blood flow through the incision typically continues, into the surgical field.
When using the distal perfusion device, the sutures required to join the end of the conduit to the coronary artery are begun, but are often initially made very loose, allowing the conduit distal end to be located some distance away from the side of the coronary artery be sutured. The conduit is thus be only partially joined to the coronary artery, while working around the distal perfusion device inserted into the incision in the coronary artery. Working around a tube protruding from the anastomosis site may provide an added, unneeded challenge to the surgeon.
The distal perfusion device can then be withdrawn, and the conduit completely joined to the coronary artery, by adding more sutures and by tightening the previously made sutures. When the distal perfusion device is withdrawn, ischemia may begin and the blood flow into the surgical field worsen. In some situations, the patency of the anastomosis is less than desirable, as the end of the conduit had become at least partially closed or even sewn shut at the anastomosis. This lack of patency is understandable, given the 1-2 millimeter inside diameter of a coronary artery, the blood flow about the anastomosis site, and the time pressure on the surgeon, which is only increased by ischemia.
What would be desirable are devices and methods for perfusing coronary arteries during the entire anastomosis procedure, allowing the anastomosis to be completely formed between a conduit and a coronary artery. What would be advantageous are devices and methods for reducing blood flow through the anastomosis site into the surgical field. Methods for maintaining patency during the anastomosis procedure would also be beneficial.